Estimate of groundwater flow and salinity contribution to the Great Salt Lake using groundwater levels and spatial analysis

Abstract

Groundwater discharge to Great Salt Lake (GSL) is difficult to quantify but represents a potentially significant source of water and salinity to the lake’s overall water budget and chemistry, respectively. Understanding groundwater and its role in the overall health of GSL is critical due to the current and historically low lake levels. We compiled existing groundwater level data in basin-fill wells around GSL and used spatial analysis methods to 1) create potentiometric-surface maps in the areas adjoining GSL, 2) calculate groundwater contributions to GSL, and 3) estimate salinity inputs from groundwater to GSL. We observed groundwater-level declines in most of the basin-fill wells from the 1980s to 2010s. These declines are consistent with historical groundwater-level trends in the Salt Lake, Tooele, Curlew, and Weber Valleys and are a consequence of aquifer overdraft associated with less than average precipitation in the basin and increased groundwater withdrawals in the GSL watershed. Using the Darcy flux equation, we calculated a groundwater flux to GSL of 313,500 acre-feet per year, substantially greater than previous estimates derived from water balance studies but consistent with estimates derived from geochemical modeling of GSL water chemistry. We calculated a salt contribution from groundwater to GSL of 1.18 million metric tons per year, which represents about 10% of the solutes derived from surface flows to GSL in 2013.